The present invention relates to dental instruments, and more particularly to amalgam carriers.
To properly fill a tooth, a dentist must carefully first form the tooth cavity by drilling the tooth to remove all decayed material. A sterilized amalgam must then be mixed and inserted into an amalgam carrier. The tooth cavity must be sterilized and the amalgam pushed into the cavity using the amalgam carrier. Excess amalgam extending from the cavity to or below the gum line is referred to as overhang and must be carefully removed with an amalgam knife or peridontia problems will develop. Although a wide variety of amalgam carriers have been developed to hold the sterilized amalgam and push the amalgam into the tooth cavity, known amalgam carriers are not without their drawbacks.
A "lever-type" amalgam carrier comprises a handle, a generally linear support arm extending from and coaxial with the handle, and a release mechanism mounted on the support arm. The release mechanism defines an amalgam-receiving bore oriented generally perpendicularly to the handle member, a plunger for forcing amalgam out of the bore, and a spring-loaded lever for moving the plunger and amalgam bore relative one another. An example of such a carrier can be seen in U.S. Pat. No. 1,797,866 entitled AMALGAM CARRIER and issued Mar. 24, 1931, to Ivory. Although providing proper amalgam placement in buccal and mesial surfaces, namely those tooth surfaces facing the cheeks and mouth centerline, and crown surfaces, lever-type carriers are extremely difficult or impossible to use when inserting an amalgam in distal and lingual surfaces, namely those surfaces opposite the mesial and buccal surfaces, respectively. Because the amalgam-receiving bore is oriented generally perpendicularly to the handle and because the dentist must work through the relatively restricted opening of a patient's mouth, axially aligning the amalgam bore with a distal or lingual surface tooth cavity is extremely difficult, and consequently the amalgam cannot be properly pushed into the tooth cavity, resulting in an inadequate filling. Occasionally, the amalgam is dropped during an attempt to insert it into a lingual surface, thereby contaminating the amalgam. This results in excessive delay when the contaminated amalgam is scrapped and a new sterilized amalgam prepared. Infrequently, a dentist will simply use the contaminated amalgam without resterilization, resulting in possible serious infection.
A second amalgam carrier is known as a "gun-type" and includes an amalgam-receiving bore, a plunger for expelling an amalgam load from the bore, and an elongated actuating mechanism for interconnecting the bore plunger with an actuating member. An example of this type of carrier can be seen in U.S. Pat. No. 2,696,670 entitled COMBINATION AMALGAM CARRIER AND PLUGGER and issued Dec. 14, 1954, to Thurman. However, because the handle and actuating member are located remotely from the amalgam-receiving bore, accurate positioning of the amalgam load with respect to the tooth cavity is difficult. Accordingly, the problems with amalgam placement and dropping discussed above are also incurred with the gun-type carrier.